On Sunday, President Donald Trumpdemanded Congress provide $5.7 billion in funding for a “steel barrier” that will be constructed along the U.S. southern border.

The latest development regarding border security shows Trump and the White House have backed down from the initial plan to build a concrete wall. The partial government shutdown entered its 17th day on Monday, as the standoff between Republicans and Democrats persists over the issue of illegal immigration.

On Friday, Trump said the shutdown could continue for “months and even years” if Democrats refuse to compromise on immigration by funding the wall. The president also said over the weekend that he “can relate” to the 800,000 federal workers affected by the shutdown who have lost pay since the government closed on Dec. 21.

Trump is weighing the possibility of bypassing Congress and declaring a “national emergency” regarding border security.

“A physical barrier — wall — creates an enduring capability that helps field personnel stop, slow down, and/or contain illegal entries,” Russ Vought, the acting director of the Office of Management and Budget, wrote in letters sent Sunday to the House Appropriations Committee chairwoman, Democratic New York Rep. Nita Lowey and its ranking member, Texas GOP Rep. Kay Granger.

On Thursday, House Democrats — who now hold the majority in that chamber of Congress — passed a series of bills to reopen the government that exclude funding for the border barrier. That bill is expected to be rejected by the Republican-controlled Senate, however.

On Sunday afternoon, Trump tweeted that Vice President Mike Pence“had a productive meeting” with congressional leaders like California Rep. Nancy Pelosi,the House Speaker, and New York Democratic Sen. Chuck Schumer.

In the same Twitter post, Trump said he believes a steel barrier on the U.S.-Mexico border would be “stronger & less obtrusive.”

V.P. Mike Pence and group had a productive meeting with the Schumer/Pelosi representatives today. Many details of Border Security were discussed. We are now planning a Steel Barrier rather than concrete. It is both stronger & less obtrusive. Good solution, and made in the U.S.A.

Democratic Washington Rep. Adam Smith, the chairman of the House Armed Services Committee, said in an interview on ABC’s This Week on Sunday that Trump technically has the legal authority to bypass Congress in order to build a border wall.

“There is a provision in law that says the president can declare an emergency,” Smith told George Stephanopoulos. “In this case, I think the president would be wide open to a court challenge saying, where is the emergency? You have to establish that in order to do this.”

According to data provided by the U.S. Customs and Border Protection agency, 396,579 arrests were made along the southwestern border in 2018 — less than the 400,751 arrests made over the previous ten years.

Trump’s vow to use his authority to build a southern barrier could also likely be challenged in court, the way his other immigration policies like the Muslim ban and asylum ban have been.